Foundation and method of constructing the same



April 10, 1945. J.v H. THORNLEY i 2373,275

FOUNDATION AND METHOD OF CONSTHUCTING THE SAME Filed Dec. 16, 1942 2 Sheets-Sheet l prl l0, 1945. 1 H, THORNLEY v 2,373,276

FOUNDATION AND METHOD OF' CONSTRUCTING THE SAME Filed Dec. 16, 1942 2 Sheets-Sheet 2 3 INVENTOR.

' high load bearing value in small diameter.

Patented Apr. 10, 1945 UNITEDV STATES- PATENT.

OFFICE FOUNDATION AND METHOD oF CoN sTaUcTrNG THE SAME Joseph H./Thornley, Evanston, Ill. Application December 16, 1 942, Serial No. 469,192

2 Claims.

The present invention relates to foundations, and to the method of constructing'same. The invention is particularly concerned with constructing caisson footing in soil of non-rock composition.

My Patent No. 1,822,550 discloses a type of foundation in which a large load may be carried inches to 30 inches, the foundation may, with the greatest simplicity of construction, develop a load bearing value as high as the load bearing strength-of the shaft or column of thecaisson The column or shaft of the caisson may be reenforced in any preferred manner to develop a This reenforcement may consist in a suitable cage of reenforcing bars and/or steel columns such as rolled shapes and/or other known or preferred forms of reenforcement. l

displacement will not occur with loading. This is well understood by those skilled in the art.

Heretofore foundations based on such strata have been constructed by sinking a caisson or about four feet in diameter by hand-digging yby a workman with a shovel to the designated stratum and there to develop an area of `footing large enough to providethe load bearing value desired according to the following formula: L=lc.a where L is the total load in pounds; `k is the safe load bearing value in pounds per square foot; (this value is fixed by the conditions of the stratum ofthe particular installation), and a is the pro- `J'ected area of footing required. The necessary area offooting may be developed by enlarging thelower end of the bore into la chamber, the

bottom of which provides the required area.

Sinking of the caisson by hand is slow and costly, and it leaves a bore of a size greater than For situations where bedrock is available at not too great a depth, the above form of caisson presents striking advantages.

However, there are situations wherebedrock is found only at relatively great depth, and the advisability of installing drilled-inrock socketedy caissons is rendered questionable'because of the great cost of reaching these extreme depths. In such cases not infrequently strata of dense materials, such as hard clay, cemented gravel or hard pan and the like, are encountered at modcrate depths. Due to lack of bonding quality of such materials, bonding ofthe sidewalls of the caisson thereto is not effective. Such strata may be encountered at depths and under conditions which would assure adequate stability and permanence for supporting the load, if direct bearing load be conned to a suitable unit value. 'The advantages of the small diameter drilled-in caisson and its ease of construction are not available within the methods of the prior art, for'support in non-rock strata.. Such supporting 'strata should be at suicient depth that its `stability'is assured. In other words,"thereshouldfbe ,sufficient depth of overlying strata thatiupthru'stcr yis necessary for the load, i. e., the shaft or co1- umn may be of excessive diameter for the load which it'is required to carry.

`I have conceived the lpossibility of installing caissons based upon stable strata such as hard clay,4 `hard pan, etc., encountered at suitable ldepths by a novel method and construction which `avoids hand digging heretofore required to sink the shaft, and which permits of the employment A ofjdrillingor machine digging for all of the caisson except the small amount required to develop the desired area of footing by the increase of 'cross section at the lower end of the shaft or bore. yAccording to the preferred practice of my invention, the shaft or bore is of so small -a diameter, preferably about `30 inches, that it may be quickly and easily sunk by machine digging either by machines, such as described in my prior patents, or by well drilling apparatus.

The hole is drilled or otherwise sunk into the desired stratum to a depth, a short predetermined distance, below the intended oor of the footing in the stratum. A

pipe forming-a liner or shaft casing is sunk into the bore to a point where itslower end is at a levelwhich is substantially the level of the top of the desired enlargement of the caisson. It

preferably seals to the desired load bearing stra- Atum to exclude watery and loose material that might enterthe bore.

`A bucket which substantially fills the bore of the hole is now lowered on a cable to the bottom of the hole. A workman may be lowered with the bucket or separately lowered later.A The top of the bucket may lnow dene approximately the level of the'bottom of the desired footing or enlargement of the bore. 'Ihe bucket may be pro-l 12. o l l 2,373,276

vided with a cage or support for convenience in raising and lowering the Workman, and for supporting him in the bore above the bucket.

The bore of the hole is large enough to admit the body of the workman with some freedom for movement. While it does not provide much vworking room, it allows the workman to stand in the hole, on, or in, the bucket, and to dislodge: or digither'soil from't'tha'side .cfslthe holewhereby it falls into the bucket. "He rides up with the r'st few bucketfuls. -He digs out a recess as soon as he can do so, whereby he may' lodge himself in the recess while the ,bucket;.is being raised' and lowered to` take thefspilaoutbf the excavation. The bucket may carryA a transor it may be a plain bucketeanddnthat event he stands in the bucket. "The bucket ispreferably of a diameter at its mouth which; substantially fills the bore so that a minimum of -material fails" outsideftheebucket whenfhefuislodges material' from ithewalls o1the-bore.`

The area of-fther' footing "(including'ithembore stratum is of densehheavysoil. diggingtool able to assist the workman to produce the enlargementl may be employed to advantage.

After the proper recess has been excavated, a cage of reenforcing rods or other reenforcement 6 may be placedrinthe recess, and likewise in the son is recognized by .fthose skilledin the art, and lsincesmethodsiof reenforcing are wllknown, no

specific treatment of this phase of the matter is .srequiredl Likewseethemethods of reenforcing the shaft L.Gr.columnof the caisson are well known, and do 15 not require specific explanation. So also anchorverse bar forming a step for hirmztoi-standzupon,

:ring-offtheytops of caissons to each other and/or Vto the superstructure is well within the skill of the art; particularly in view of my prior patent ,i aforesaid.

20 It may be observed that particularly in the scribe, in connectiondwith'i theaccompan'ying vaowdrawingsf-v.- aspeccfembodiment rfoiwmy-f invention,

In theidrawings:

"Fgure liS.. a:verticalcsectionushowing the :preliminaryfdrilling: ofaainholezzinto the stratumfdemay convenientlyibe operated*bye-compressed; 35-vsignedftoreceiveltheiload;anfrthe casingxot'the lair or electricity-ifromtherhead-f-oif the'fcai'sson.

side lthe space off the-original boref 'ftheeraising and! lowering; ofi-the 'fr-bucket;doeswnot interfere with his activities.

1 The essence ofI ithefideav is-'toproject orextend the holeywhich lis preferably-mf -'so`sml1 arbore a shovel,4 to*A a` ipbint'belowffthefdesired regioneof I initial enlargement;*ldislodgefspil from' the-wall of the hole: anda* allow-i1; todrop into-*thas space A aiorded by- 'theflowerend'of" the\bore;-aIidthen Y. i the 'spoil --is= iremoved-ifromi Ii-ts4 lodgmenthinthe lowerend -o'the bore. '-The buckevsionlyllone t Ymeans for fdoingthevlatter. JAA power-operating digger of theftype'disciosed -irrmypliorpatent or -other^means Xmay berlused'ilforfthatgipurpose. Y

55 .caisson tiedfto I thea ends of: adi acentv caissonaand l -A1so, itis-to beobserved thatlowerin'gmfman `into the boreto dislodgespoil for! thepurposesof creating the `-desired:enlargementwhilemit=issthe preferred 4procedure is fbutsoneeway of f accomplishing thisy end. i-vAnfexpanding rea-menorbther device xcperatedfffromrf-thei:topfof'the lholewmay be employed todoipartwrfall of thaworkbfidislodging spoil" for theipurpose .of -iormingtheeenlargement. Thisg'.- vhowever;"requires 1'- heavyaand It is generally l .not :desirable l to: dist-.urbane stratum '-inf i which ithefooting Yise-to bearestedany more than necessary to formijtheidesiredfspaee.

details'of the procedure arevsiibjecttofandffare capable of'variation `within f theiskillof'f-the art.

borevof the samedown"l toisaidlstratum; Y,

FigureZ is a venticalsection .througlitheebuicket and supporting-.bail for raisingtthefspoil;

r@Figure .3' iisia:idiagrammatic;zillustraitionirofr a uo: compressedahr operated diggingfatool;

l :largement byiafworkmaniloweredrinto theibore;

:Figure isfazvertical.; seetionzshowingzthe-bore that a workman" could not*dig*fdownwarzilwwithtiiA with ther enlargedgchamben` attthelowerxendfor rformingcthefextendedipedestal;` Y

Figure: Suis: a 1horizontal;fcrossesectionalfview :onsthei-liI-ieB--B; oii Egure 5; y

Figure 7 shows the boreiandfexcavationfotiig bozurefswithaods andffreeniorcing. cagefinpplace;

frFgureiS is afcrossesectionalfview, takengon-rthe lineB-BofFigure';

:.1 Eixure'Sl-isaa verticalfgelevationof apartlof the :.inished,v `foundationswithu ,thei uppere end Fofgithe "oringr through:,the@shaft.fcfathescaisson or.pile;

LEfgure ll-isalike vieu; ofvyanotheroptional construction.,.employingtwossteel reenforcingtbars `.orTk a. aslit, I-beam reenforcement;and, v l

, Figure 12ishows a detail .fofj constructionofthe 'hasingle drilledfin ca-issonsherein illustrated .and 'described ,preferably constitutes f one; ofr a lurality of suchstructureswhich arecon'neeted tpgthen either-through partsN offth'efOridation structure, asby tie'fbeamsl connecting twoiolmore Y such drilled-in caissons, .012 alternatively', through :the: superstructure whichmay Ybeet. 'ste'el or. reenforced concretejframefas desiredl" IIn certainjsituations,"bedrock is at4 ,Se great; a

upon a stable stratum of dense material such as clay or the like, which may be located at a reasonable depth and be of. a character suitable tosustain a fairly high unit loading. Thus in Figure 1 assume that a distance .A below the surface there may be encountered a layer of dense clay which extends a distance B to underlying rock. Assume by way of example that the distance A is 80 feet and the distance Bis 40 feet, a stable foundation may be secured by producing a relatively large footing within the stratum of clay. I-Ieretofore the smallest caisson which it hasbeen the practice to sink under such conditions is required to be about four feet in diameter in order to permit hand digging by workmen operating in the caisson to sink it to the required depth.

According to my invention, I proceed first, after test or exploratory drillings have determined the character of the underlying soil andthe strata thereof, to drill by suitable mechanical mechanism which preferably is of the oil well drilling type or of the mechanical digger type, a shaft which is projected down into the layer a suitable depth. The diameter of this bore is about 24 to 30 inches, preferably the-latter. A liner, which may be made in sections, if removable or continuous if allowed to remain, is projected from the surface of the ground down into the top ofthe stratum, to maintain or case the bore and to shut olf the drainage of water into the hole. The bottom 3 of the bore I lies a suitable distance below the level 4 which level 4 is selected as the level of the bottom of the enlarged footing ofthe pile or caisson. A bucket 5 with supporting bail vI5 is lowered as by a cable 1 into the recess 8 which is formed below the level 4y of the desired footing. The bucket may be of any desired construction. Preferably it comprises the bail B having hooks 9, 9, see the detail of Figure 12, projecting into sockets I0, I formed on the inner walls of the bucket 5, 5. These hooks, if desired, may bedetachable or the ends of the hooks may be curved up inside of the sockets ID, I0, s0 as to prevent their removal. A suitable step or cross piece I2 is located adjacent the top of the bucket. This step may be placed across the mouth of the bucket if desired and may be removable, or, as shown in Figures 2' and 12, the step may be formed as a part of the bail, and in that event may be removable in order to permit removal of the hooks 9 from the socket I0, as shown in Figure 12. This detail of construction is optional. In the specific detail shown in Figure 12, the step I2 forms a strut between the two sides I3, I3 of the bail, which bail is preferably a round rod. The two side members of the bail I3, I3 are extended upwardly and converge at I4 to an eye I5 by which attachment to the cable 1 may readily be made. A cross brace I6 between the upper ends of the side members I3, I3 serve to prevent collapse of the two members I3, I3 towards each other, and forms a convenient hand hold for the workman when he is lowered or raised with the bucket. The bail thus forms a cage within which the workman may be supported and he may steady himself in the central position in the cage. A suitable ring or hook I'I may be provided on the outside of the bottom of the bucket whereby the same may be readily inverted for discharging the contents of the bucket. The bucket and cage with a workman indicated at I8 is lowered into the bore I with the bucket disposed in the recess 8 and preferably resting upon the bottom 3 of the same. The workman I8 is then in position to dislodge dirt from the side walls of the bore below the lower .end of the liner 2. .Thisdislodged material or spoil drops by gravity into thebucket 5, andiwhen the bucket is filled, the bucket and workman are lconical chamber 22 thereby defined is preferably about' 45'. although this is subject to optional variation. The workman may be supplied with electric light from the surface, and may be in telephonic connection if desired, and to expedite his work he may be supplied with a power digging tool provided with a blade and air hammer, such as is indicated more or less diagrammatically in Figure 3. Such power operated digging tool is known in the prior art and need not here be described.

When the excavation is completed, the conical chamber 22 is of a suitable size and form to define an enlarged footing or pedestal for thecaiss-on which is then cast in place. The size and shape of the enlarged chamber may be widely varied to suit conditions or the convenience of the workman. An advantageous form is the generally conical shape indicated in the drawings. For example, the diameter of the enlargement may be approximately l0 feet. The distance between the floor 4 and the-bottom of casing may be approximately 5 to 6 feet and the height of the cylindrical wall 20 about 11/2 'to 2 feet. These dimensions are To'ptional, but give a fair idea of a typical installation. The eifective area of the enlargement should, for the .above dimensions, be about l5 times the area of cross section of the bore. Obviously it may lbe made greater or less as conditions orv the option ofthe designer may determine. The casing 2 may be left in place or it may be withdrawn, as the caisson is completed. Reenforcing rods indicated at 23, 23 in Figure 7 are formed in the shape of a conical cage, and a series of radial reenforcing rods 24, 24 are placed adjacent the bottom 4 of the recess particularly to reenforce against the stress produced by upward thrust on the bottom surface 4. The rods 23, 24 may be reenforced by circumferential reenforcement in a manner known to those skilled in the art. The shaft or main body of the caisson may be reenforced by a circular cage .25, extending throughout the length of the shaft I, or any desired part thereof, this cage ferential members in a manner well known in consisting of longitudinal members and circumthe art.

If a greater load is to be carried on the caisson, a reenforcement consisting of an I-shaped beam 26, shown in cross-section in Figure 10, may be extended down through the shaft of the caisson and into the footing thereof. The area of the footing varies with the load bearing value of the soil and with the load to be supported.

Any desired form of reenforcement of the caisson may be employed, and the metal casing 2 may be utilized in part to carry the load, or it may be neglected, or it may be withdrawn upon completing the caisson. In Figure 11,'I have shown a reenforcement comprising a slit I-beam with the anges placed back to back, as indicated at 21,21, in Figure 11.

When the reenforcement has .been properly disposed in the bore and in the enlarged excava- ',.tionf '2 2, `concrete Sis .poured to ll the extensions,

the chamber '22 :andi the bore .I. 'The caisson rests in .substantially undisturbed material, and Yis'therefore firmly supported.. s f' At its upper .end the ,caisson lmay fber cast `iwi an integral head 28,.swhich vbe joinedhy beamsv 29 to adjacent .tops or` heads of other-:caissons or piles. 4Reenforcing@rods 30,;are1projected `above the head 28 forfconnectionzto the superstructure whereI the superstructure .has 'a .reenforced concrete frame. Obviously,.if asteelibeam, such as y28, indicated in lligureilO, is. utilized, it

`may loe-'suitably headed at thefupper end-,. to

receive theload ofthe superstructure, 'andftofbe tied, yeither fby the superstructure, or by..inde pendent Vties Vto other. .piles lor caissons inl the foundation. The enlargement S32 may be shaped Vin any vdesired form. Preferably such ia'form as presents eiective resistance to displacement vor iiow 4.of the :material around it is'selectecl.y The loose dirt iscleared out `of .the sextensionSmefore concrete is poured.

The diameter and thicknessl of thepedestal 32 may be variedto suit'the circumstances Vof lthe load to be supported. Preferably .the top surface `of the conical enlargement is formed at .an .angle of approximately 45 although this .obviously is optional. A suitable 'thickness of the rim of .the vpedestal is desirable to prevent breakage thereof.

The bore extension 33 carries l.its own proportionreamer or the like operated from the top-of the.

hole, 4some of the .material maybe dislodged 4into the bucket and the same raised. Alternatively,

"material may be mechanically dislodged from the -boretofthe v'hole into the recess 8, .and'extracted 4tl'iereiroi'n vby an `open ended digging tool such as is fdescribed in Amy prior patent above referred to. The essence' of vthe operation is vtoproject the bore down below the place of desired enlargeof the caisson. The load which may be Acarried by a caisson of this character may be very great. I .do not intend to be limited to the details shown or described nor to the specific procedure recited except as the same are made to appear essential Within the termsof the following claims.

` I claim:

1. Method of making a slender concrete pile with van enlarged footing which consists in drillin'g va relatively vsmall diameter rbore from the ground surface into a dense stable non-rock stratum disposed at a substantial distance below the ground surface, .lowering a .bucket into the lower end of 4the bore to receive spoil, digging .out the side walls of the bore vabove said bucket to forman enlargement Within .said dense stratum, .and permitting the dislodgedand loosened spoil to fall into the bucket, raising said bucket to remove the rdislodged and loose spoil, whereby 'a Aslender `bore enlarged intermediate its ends `within said Vdense stratum with substantially no vloose spcilin the bore or in the enlargement is provided, and iilling the bore, including the enlargement With concrete.

2. The method of claim 1, wherein the bore is notsubstantially larger than 30" in diameter and .the dense :stratum within which the enlargement .is `formed is -of lthe class consisting of "hardpan, cemented gravel and vheavy clay. A v JOSEPH H. THORNLEY. 

